Three patients with congestive cardiomyopathy are reported in whom high neutralizing antibody titres to Coxsackie B viruses were detected. At post-mortem examination, all three had histologically demonstrable chronic inflammation of the myocardium. The hearts of ten patients dying in cardiac failure due to other causes showed no comparable inflammatory infiltration. This provides further evidence that Coxsackie B viral myocarditis is involved in the pathogenesis of some cases of dilated cardiomyopathy. One patient also had pulmonary veno-occlusive disease. This has been reported in association with myocarditis once previously in an infant. A viral aetiology has been postulated. It seems likely in this patient to have also been due to a Coxsackie B virus.